Influence of pregnancy on the risk for cardiac events in patients with hereditary long QT syndrome

Background-The effects of pregnancy on women with the hereditary long QT syndrome are currently unknown. The appropriate medical management of pregnant patients with the long QT syndrome has not been established. Methods and Results-The study was a retrospective analysis of the 422 women (111 probands affected with the long QT syndrome and 311 first-degree relatives) enrolled in the long QT syndrome registry who had one or more pregnancies. The first-degree relatives were classified as affected (QTc >0.47), borderline (QTc=0.45 to 0.47), and unaffected (QTc <0.45). Cardiac events were defined as the combined incidence of long QT syndrome-related death, aborted cardiac arrest, and syncope. The incidence of cardiac events was compared during equal prepregnancy, pregnancy, and postpartum intervals (40 weeks each). Multivariate logistic regression analysis was performed by use of a mixed-effects model to identify independent predictors of cardiac events among probands. The pregnancy and postpartum intervals were not associated with cardiac events among first-degree relatives. The postpartum interval was independently associated with cardiac events among probands (odds ratio [OR], 40.8; 95% confidence interval [CI], 3.1 to 540; P=.01); the pregnancy interval was not associated with cardiac events. Treatment with β-adrenergic blockers was independently associated with a decrease in the risk for cardiac events among probands (OR, 0.023; 95% CI, 0.001 to 0.44; P=.01). Conclusions- The postpartum interval is associated with a significant increase in risk for cardiac events among probands with the long QT syndrome but not among first- degree relatives. Prophylactic treatment with β-adrenergic blockers should be continued during the pregnancy and postpartum intervals in probands with the long QT syndrome.